May 21, 1901
First automobile speed limit in US
Colonial speed limits have been around since Boston passed the first one in 1757 for horses and horse-drawn vehibles. On May 21, 1901, Connecticut became the first state to pass speed limits for automobiles. City driving was limited to 12 mph, but drivers could go up to 15 mph once they left the city limits.
http://www.wired.com/science/discoveries/news/2008/05/dayintech_0521